Salina Blues Population Survey 2013Apr 15th, 2013 | By DirectorFred | Category: Featured article
Our triennial survey of the restored Blue Iguana population in the Salina Reserve is just wrapping up. All through March, our team of eight walked every segment of trail in our survey zones, twice a day for eighteen active survey days, logging every iguana detected using a distance sampling protocol.
That all added up to 441 iguana detection events, and a huge mound of data now organized in an impressive spreadsheet and about to undergo preliminary analysis. We are just clarifying the last few mysteries out there in the Salina, and should be calling the job done within the next day or two.
Some iguanas were easier to see than others – the trickiest ones ran from us before we even saw them. Others stayed motionless and blended into the rocks…
Sometimes all we could see was a little blue head…
But the dominant males, like BRB here who rules the northern “Zone A” just treated us like we weren’t even there.
What a team we had!
Team 1: Fred Burton, Phil So
Team 2: Doug Bell, Leslie Latt
Team 3: Laura Casolino, Craig Stine
Tagging and retreats mapping Team: Stacy Whitaker, Charles Lee
Our first impressions from the results are mostly good – the population looks to be holding steady since we last did this survey in 2010. Some iguanas have emigrated, some have immigrated, and some of the ones we released between surveys have stayed in the core areas.
We were happy to see not a single invasive Green Iguana out there – hopefully the environment is just too harsh for them to colonize. We were less happy to see quite a few rats – these seem to be going through a boom cycle island wide, and we know they sometimes gnaw off the ends of the iguanas tails.
We were a bit disappointed not to see wild born Blues hatchlings, yearlings or two-year olds, among the iguanas we saw. We do know the population is breeding, but it seems that the numbers of hatchlings emerging each year may be too few to surmount the natural pressure of snake predation, and the diluting effect of hatchling migration. As the released females keep growing, they will lay more and more eggs each year, so maybe next time in 2016, we will start to see the hoped-for evidence of recruitment!
(Iguana photos all by Douglas Bell)